Magnetic resonance methods as a prognostic tool for the biorelevant behavior of xanthan tablets

Hydrophilic matrix tablets with controlled drug release have been used extensively as one of the most successful oral drug delivery systems for optimizing therapeutic efficacy. In this work, magnetic resonance imaging (MRI) is used to study the influence of various pHs and mechanical stresses caused by medium flow (at rest, 80, or 150 mL/min) on swelling and on pentoxifylline release from xanthan (Xan) tablets. Moreover, a bimodal MRI system with simultaneous release testing enables measurements of hydrogel thickness and drug release, both under the same experimental conditions and at the same time. The results show that in water, the hydrogel structure is weaker and less resistant to erosion than the Xan structure in the acid medium. Different hydrogel structures affect drug release with erosion controlled release in water and diffusion controlled release in the acid medium. Mechanical stress simulating gastrointestinal contraction has no effect on the hard hydrogel in the acid medium where the release is independent of the tested stress, while it affects the release from the weak hydrogel in water with faster release under high stress. Our findings suggest that simultaneous MR imaging and drug release from matrix tablets together provide a valuable prognostic tool for prolonged drug delivery design

Application of magnetic resonance imaging for research of anatomy and moisture content of wood

Feasibility of nuclear magnetic resonance (nMR) was tested for research of anatomy and moisture content of wood. A three m high living beech tree (Fagus sylvatica L.) was imaged by magnetic resonance using the 3D spin-echo microscopic imaging technique at isotropic spatial resolution of 100 mm to follow structural changes in the topped branch caused by healing response mechanisms of the tree. Conventional light microscopy was also employed to verify tree structures detected on MR images. Conventional light microscopy revealed anatomical structures and three year age of the tree branch. MR images clearly showed pith, radially oriented xylem rays, early wood vessels with a delineated border between early and late wood, as well as the cambial zone with current xylem and phloem growth increment. We studied water concentration in the branch and the depth of dehydration formed in 22 hours after the mechanical injury. The dehydrated region extended to the mm depth from the wound location. First passive response of the injured branch tissue reflects in the initial decrease of the moisture content that was detected by MR imaging. Finally, we processed 3D MR microscopy data by the ImageJ image processing program to depict the spatial water concentration in the tree branch and to determine tissues with high water content

Influence of mechanical wounding and compartmentalization mechanism on the suppression of invasive plant species using the example of Cherry Laurel (Prunus laurocerasus)

Natural habitats increasingly face the introduction and spread of non-native species. Under the right conditions, non-native species can become invasive over time. This issue is now being addressed by many experts and researchers who are using and developing various approaches and methods to limit and eliminate or suppress problematic plant species. Many invasive plants are already spreading uncontrollably in urban and forestry areas, causing health hazards, environmental and economic damage and negatively impacting natural ecosystems. The use of chemical agents is generally limited, so our only option to control and suppress the problematic species is mechanical removal. In this research suppression by tree stem wounding, i.e., incomplete girdling, was used. This type of injury causes the plant to lose its vitality, become weaker after first year and then die within a few years. Using a research approach, we chronologically monitored the response of cherry laurel (Prunus laurocerasus L.) stem tissue to mechanical wounding of the incomplete girdling. Magnetic resonance imaging (MRI) and light microscopy were used for monitoring moisture content and anatomical changes in different periods after injury. The results of the study showed that cherry laurel, with an intense wound tissue response and other changes, is a species with good compartmentalization potential. The rapid and intense tissue response to injury requires high energy and nutrient consumption and consequently leads to a loss of vigour and mechanical stability, which may result in plant destruction. Results revealed that mechanical wounding by incomplete girdling is a successful method for suppression of non-native and invasive cherry laure

Application of magnetic resonance imaging for research of anatomy and moisture content of wood

Preverjena je bila uporaba jedrske magnetne resonance (Nmr) za raziskave anatomije in vlažnosti lesa. Na tri metre visoki živi bukvi (Fagus sylvatica L.) smo uporabili 3d spin-echo mr-mikroskopsko tehniko slikanja s prostorsko resolucijo 100 mm in opazovali strukturo odrezane vejice ter spremljali dinamični odziv drevesa na mehansko poškodbo. Za potrditev struktur, vidnih na slikah, smo uporabili svetlobno mikroskopijo. Svetlobna mikroskopija je razkrila anatomsko zgradbo in triletno starost vejice bukve. Slike so jasno razkrile stržen, radialno orientirane večredne ksilemske trakove, traheje ranega lesa, vključno z mejo med ranim in kasnim lesom, kot tudi kambijevo cono s tekočim ksilemskim in floemskim prirastkom. Preučevali smo koncentracijo vode v vejici in globino dehidracije, ki je nastala v 22-tih urah po poškodbi in je segala v globino približno 5 mm od poškodbe. Hitra izguba vlažnosti odseva začetni pasivni odziv prizadetega tkiva. S pomočjo 3d mikroskopije in računalniškega programa Imagej nam je uspelo izdelati prostorski model vode v lesu, ki prikazuje tkiva v vejici z značilno višjo vlažnostjo.Feasibility of nuclear magnetic resonance (nMR) was tested for research of anatomy and moisture content of wood. A three m high living beech tree (Fagus sylvatica L.) was imaged by magnetic resonance using the 3D spin-echo microscopic imaging technique at isotropic spatial resolution of 100 mm to follow structural changes in the topped branch caused by healing response mechanisms of the tree. Conventional light microscopy was also employed to verify tree structures detected on MR images. Conventional light microscopy revealed anatomical structures and three year age of the tree branch. MR images clearly showed pith, radially oriented xylem rays, early wood vessels with a delineated border between early and late wood, as well as the cambial zone with current xylem and phloem growth increment. We studied water concentration in the branch and the depth of dehydration formed in 22 hours after the mechanical injury. The dehydrated region extended to the mm depth from the wound location. First passive response of the injured branch tissue reflects in the initial decrease of the moisture content that was detected by MR imaging. Finally, we processed 3D MR microscopy data by the ImageJ image processing program to depict the spatial water concentration in the tree branch and to determine tissues with high water content

Uporaba magnetno resonančnega slikanja za raziskave anatomije in vlažnosti lesa

Preverjena je bila uporaba jedrske magnetne resonance (Nmr) za raziskave anatomije in vlažnosti lesa. Na tri metre visoki živi bukvi (Fagus sylvatica L.) smo uporabili 3d spin-echo mr-mikroskopsko tehniko slikanja s prostorsko resolucijo 100 mm in opazovali strukturo odrezane vejice ter spremljali dinamični odziv drevesa na mehansko poškodbo. Za potrditev struktur, vidnih na slikah, smo uporabili svetlobno mikroskopijo. Svetlobna mikroskopija je razkrila anatomsko zgradbo in triletno starost vejice bukve. Slike so jasno razkrile stržen, radialno orientirane večredne ksilemske trakove, traheje ranega lesa, vključno z mejo med ranim in kasnim lesom, kot tudi kambijevo cono s tekočim ksilemskim in floemskim prirastkom. Preučevali smo koncentracijo vode v vejici in globino dehidracije, ki je nastala v 22-tih urah po poškodbi in je segala v globino približno 5 mm od poškodbe. Hitra izguba vlažnosti odseva začetni pasivni odziv prizadetega tkiva. S pomočjo 3d mikroskopije in računalniškega programa Imagej nam je uspelo izdelati prostorski model vode v lesu, ki prikazuje tkiva v vejici z značilno višjo vlažnostjo.Feasibility of nuclear magnetic resonance (nMR) was tested for research of anatomy and moisture content of wood. A three m high living beech tree (Fagus sylvatica L.) was imaged by magnetic resonance using the 3D spin-echo microscopic imaging technique at isotropic spatial resolution of 100 mm to follow structural changes in the topped branch caused by healing response mechanisms of the tree. Conventional light microscopy was also employed to verify tree structures detected on MR images. Conventional light microscopy revealed anatomical structures and three year age of the tree branch. MR images clearly showed pith, radially oriented xylem rays, early wood vessels with a delineated border between early and late wood, as well as the cambial zone with current xylem and phloem growth increment. We studied water concentration in the branch and the depth of dehydration formed in 22 hours after the mechanical injury. The dehydrated region extended to the mm depth from the wound location. First passive response of the injured branch tissue reflects in the initial decrease of the moisture content that was detected by MR imaging. Finally, we processed 3D MR microscopy data by the ImageJ image processing program to depict the spatial water concentration in the tree branch and to determine tissues with high water content

Research of wood structure by three dimensional magnetic resonance imaging

V prispevku je opisana uporaba tri-dimenzionalnega magnetno resonančnega slikanja (3D MRI) na primeru vejice hrasta doba. Tridimenzionalni MR modeli in virtualni prečni prerez vejice razkrivajo, da imajo kompleksi vazicentričnih traheid in trahej, ksilemski trakovi, stržen in tkiva v neposredni bližini kambijeve cone večji MR signal in s tem tudi večjo vlažnost kot skorja in libriformska vlakna. Prednost 3D MRI je, da pri slikanju hkrati pridobimo slike z odlično prostorsko ločljivostjo, hkrati pa tudi pripadajoče podatke o prostorski porazdelitvi vode v materialu. 3D MRI dopolnjuje druge mikroskopske tehnike v lesarski znanosti.Application of three dimensional magnetic resonance imaging (3D MRI) for imaging of pedunculate oak is demonstrated in this contribution. Three-dimensional volume rendered MR images and virtual cross section showed that complexes of vasicentric tracheids and vessels, xylem rays and tissues adjacent to cambial zone had higher MR signal and hence higher water content than bark and libriform fibers. Advantage of 3D MRI is in that with a single scan, high resolution images and information on moisture content can be obtained. MRI complements other forms of microscopy in wood science

A new approach combining different MRI methods to provide detailed view on 2 swelling dynamics of xanthan tablets influencing drug release at different pH and 3 ionic strength

The key element in drug release from hydrophilic matrix tablets is the gel layer that regulates the penetration of water and controls drug dissolution and diffusion. We have selected magnetic resonance imaging (MRI) as the method of choice for visualizing the dynamic processes occurring during the swelling of xanthan tablets in a variety of media. The aims were (i) to develop a new method using MRI for accurate determination of penetration, swelling and erosion fronts, (ii) to investigate the effects of pH and ionic strength on swelling, and (iii) to study the influence of structural changes in xanthan gel on drug release. Two dimensional (2D) MRI and one dimensional single point imaging (SPI) of swollen xanthan tablets were recorded, together with T2 mapping. The border between dry and hydrated glassy xanthan-the penetration front-was determined from 1D SPI signal intensity profiles. The erosion front was obtained from signal intensity profiles of 2D MR images. The swelling front, where xanthan is transformed from a glassy to a rubbery state (gel formation), was determined from T2 profiles. Further, the new combination of MRI methods for swelling front determination enables to explain the appearance of the unusual Ćbright frontĆ observed on 2D MR images in tablets swollen in HCl pH 1.2 media, which represents the position of swelling front. All six media studied, differing in pH and ionic strength, penetrate through the whole tablet in 4 h 0.3 h, but formation of the gel layer is significantly delayed. Unexpectedly, the position of the swelling front was the same, independently of the different xanthan gel structures formed under different conditions of pH and ionic strength. The position of the erosion front, on the other hand, is strongly dependent on pH and ionic strength, as reflected in different thicknesses of the gel layers. The latter are seen to be the consequence of the different hydrodynamic radii of the xanthan molecules, which affect the drug release kinetics. The slowest release of pentoxifylline was observed in water where the thickest gel was formed, whereas the fastest release was observed in HCl pH 1.2, in which the gel layer was thinnest. Moreover, experiments simulating physiological conditions showed that changes of pH and ionic strength influence the xanthan gel structure relatively quickly, and consequently the drug release kinetics. It is therefore concluded that drug release is greatly influenced by changes in the xanthan molecular conformation, as reflected in changed thickness of the gel layer. A new method utilizing combination of SPI, multi-echo MRI and T2 mapping eliminates the limitations of standard methods used in previous studies for determining moving fronts and improves current understanding of the dynamic processes involved in polymer swelling